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PRISM Manual | RunningPRISM / ComputingSteady-stateAndTransientProbabilities 
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    <p><a class='wikilink' href='StartingPRISM.html'>Running PRISM</a> /
</p><h1>Computing Steady-state And Transient Probabilities</h1>

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<p>If the model is a CTMC or DTMC, it is possible to compute corresponding vectors of
steady-state or transient probabilities directly
(rather than indirectly by analysing a property which requires their computation).
From the GUI, select an option from the "Model | Compute" menu.
For transient probabilities, you will be asked to supply the
time value for which you wish to compute probabilities.
From the command-line, add the <code>-steadystate</code> (or <code>-ss</code>) switch:
</p>
<div class='vspace'></div>
<div class='sourceblock ' id='sourceblock1'>
  <div class='sourceblocktext'><div class="shell"><span style="font-weight:bold;">prism poll2.sm -ss</span><br/>
</div></div>
  <div class='sourceblocklink'><a href='ComputingSteady-stateAndTransientProbabilities@action=sourceblock&amp;num=1' type='text/plain'>[&#036;[Get Code]]</a></div>
</div>

<p class='vspace'>for steady-state probabilities or the <code>-transient</code> (or <code>-tr</code>) switch:
</p>
<div class='vspace'></div>
<div class='sourceblock ' id='sourceblock2'>
  <div class='sourceblocktext'><div class="shell"><span style="font-weight:bold;">prism poll2.sm -tr 2.0</span><br/>
</div></div>
  <div class='sourceblocklink'><a href='ComputingSteady-stateAndTransientProbabilities@action=sourceblock&amp;num=2' type='text/plain'>[&#036;[Get Code]]</a></div>
</div>

<p class='vspace'>for transient probabilities, again specifying a time value in the latter case.
The probabilities are computed for all states of the model and displayed,
either on the screen (from the command-line) or in the log (from the GUI).
</p>
<p class='vspace'>From the command-line, a few additional options are available.
It also possible to send the probability distribution to a file,
rather than the screen, using the <code>-exportsteadystate</code> (or <code>-exportss</code>)
and <code>-exporttransient</code> (or <code>-exporttr</code>) switches:
</p>
<div class='vspace'></div>
<div class='sourceblock ' id='sourceblock3'>
  <div class='sourceblocktext'><div class="shell"><span style="font-weight:bold;">prism poll2.sm -ss -exportss poll2-ss.txt</span><br/>
<span style="font-weight:bold;">prism poll2.sm -tr 2.0 -exporttr poll2-tr2.txt</span><br/>
</div></div>
  <div class='sourceblocklink'><a href='ComputingSteady-stateAndTransientProbabilities@action=sourceblock&amp;num=3' type='text/plain'>[&#036;[Get Code]]</a></div>
</div>

<p class='vspace'>You can also request that the probability vectors exported are in Matlab format by adding the <code>-exportmatlab</code> switch.
</p>
<p class='vspace'>By default, for both steady-state and transient probability computation,
PRISM assumes that the initial probability distribution of the CTMC is
an equiprobable choice over the set of initial states.
When computing transient probabilities from the command-line, you can override this and provide a specific initial distribution. This is done using the <code>-importinitdist</code> switch. The format for this imported distribution is identical to the ones exported by PRISM, i.e. simply a list of probabilities for all states separated by new lines. For example, this:
</p>
<div class='vspace'></div>
<div class='sourceblock ' id='sourceblock4'>
  <div class='sourceblocktext'><div class="shell"><span style="font-weight:bold;">prism poll2.sm -tr 1.0 -exporttr poll2-tr1.txt</span><br/>
<span style="font-weight:bold;">prism poll2.sm -tr 1.0 -importinitdist poll2-tr1.txt -exporttr poll2-tr2.txt</span><br/>
</div></div>
  <div class='sourceblocklink'><a href='ComputingSteady-stateAndTransientProbabilities@action=sourceblock&amp;num=4' type='text/plain'>[&#036;[Get Code]]</a></div>
</div>

<p class='vspace'>is (essentially) equivalent to this:
</p>
<div class='vspace'></div>
<div class='sourceblock ' id='sourceblock5'>
  <div class='sourceblocktext'><div class="shell"><span style="font-weight:bold;">prism poll2.sm -tr 2.0 -exporttr poll2-tr2.txt</span><br/>
</div></div>
  <div class='sourceblocklink'><a href='ComputingSteady-stateAndTransientProbabilities@action=sourceblock&amp;num=5' type='text/plain'>[&#036;[Get Code]]</a></div>
</div>

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